Screen printing has long been used for the printing of images on T-shirts, apparel of all sorts, and cloth and synthetic fabrics generally. The use of screen printing processes have provided for the placement of artful and decorative images of a wide variety on wearing apparel.
A typical screen printing process comprises several steps. First a photoemulsion is applied to a screen. The screen is a cloth or synthetic fabric with a thread count of 80 to 300 threads per inch. A coat of photoemulsion is applied to the screen by covering one side of the screen with photoemulsion and then wiping away the excess with a squeegee. This process is generally repeated for the opposing side of the screen, with possibly two coats of photoemulsion applied to each side of the screen. The screen coated with photoemulsion forms a stencil for use in printing.
A decorative image is then formed on a sheet, or film, of an acetate/silver material. A black opaque image in the shape of the desired decorative image is formed on the film using methods known in the art. This film is then placed over the screen coated with the photoemulsion, and the screen is exposed to ultraviolet radiation. The portion of the screen corresponding to the design is shielded from the ultraviolet radiation because the black opaque image is impervious to ultraviolet radiation. The areas of photoemulsion exposed to the ultraviolet radiation, however, harden and become water insoluble. The photoemulsion on the screen not exposed to ultraviolet radiation is then washed away, leaving a screen with hardened photoemulsion coat forming the negative of the desired decoration.
The screen is then placed over the substrate to be printed, and ink is forced through the fine mesh of the screen and onto the substrate. This is done by covering the screen with ink and wiping a squeegee across the screen. The hardened photoemulsion prevents ink from passing through the screen except at the location of the decorative image. The amount of ink forced through the screen depends, in part, on the particular squeegee used and the method of use of the squeegee. A harder squeegee tends to deposit more ink on the substrate. Lowering the angle of the squeegee to the screen also tends to deposit more ink on the substrate, as does moving the squeegee across the screen at a slower rate. The shape of the squeegee blade also varies the amount of ink deposited on the substrate.
After the substrate is printed with the decorative design, the substrate is heated to dry the ink. Plastisol inks have been used so that fusion of the plastisol fuses the ink.
This process may be repeated multiple times for a single substrate. Repeating the process using different colored inks allows for a large variety of designs and images. The ease of the process allows for large numbers of prints to be easily made. The ease of the process, however, also allows designs prepared by one party to be easily copied by a multiplicity of other parties.
The above-described process also does not allow for well defined three dimensional images. A flat piece of cloth will exhibit a flat decorative image as the ink generally lies flat on the surface of the substrate. The decorative image therefore will be generally the same no matter at what angle the image is viewed. Furthermore, because the printed image is flat, the surface texture of the image will also generally be flat. Thus, the above-described process is greatly limited in not allowing the image to be enjoyed both visually in three dimensions and through the sense of touch.